Good points Dweste.

The tunnels and the bridges are the choke points. If by chance that you could get past these, most of the canyon country is wide open, albeit mountainous but the elevation is fairly low.

Following the roadway which follows the river is the best bet and although the highway may be unsuitable for vehicles, foot traffic might be ok. That said, there are still a few areas of the highway that hug some narrow spots and rock slides could make the highway completely impassable.

Given that, getting home via land would be impossible and a person would be better off finding refuge in a small town or village if possible.

I'll have to take some pictures on Friday on the way up that will give a better visualization of the area and terrain.